1. Field of the Invention
The present invention relates to an apparatus for sealing a semiconductor package by using a method of suppressing attenuation of illuminance of ultraviolet rays.
2. Description of the Related Art
The inventors know a method and an apparatus for sealing a semiconductor package. The description will be directed to such the known method and apparatus for sealing a semiconductor package made of a ultraviolet-ray-curing type resin (resin to be cured through the effect of radiation of ultraviolet rays).
In implementing the sealing method, there is provided a metallic package base as a fundamental base, on which a semiconductor package is placed. The ultraviolet-ray-curing type resin is coated on the semiconductor package. Then, an operator picks a lid with a pincette and puts the lid on a right position of the semiconductor package as he or she is visually making sure of the position. Next, the operator turns on a ultraviolet ray emitting instrument located above the semiconductor package with his one hand as applying a certain amount of pressure on the lid with the pincette in his other hand. The operator keeps the pressing state for a certain amount of time while the ultraviolet ray emitting instrument applies ultraviolet rays to the semiconductor package. Since the ultraviolet ray emitting instrument is located above the semiconductor package, the ultraviolet rays are applied to the semiconductor package through the atmosphere.
The foregoing method, however, has the following disadvantages.
(1) In case of keeping an estimated optimal distance for obtaining an optimal illuminance of the ultraviolet rays, the physical constraint resulting from a conveying system, for example, may often keep the actual distance between the ultraviolet ray emitting instrument and the to-be-applied surface longer than the estimated optimal distance. Since the illuminance of the ultraviolet rays is in inverse proportion to the distance, the illuminance is made lower by the difference between the actual distance and the estimated optimal distance, resulting in requiring a longer emitting time until the resin is cured.
(2) Since the positioning and pressurizing of the lid are done manually with the pincette, it takes a long time to do the positioning and the pressurizing. And, the lid-set position and applied pressure are so variable that the sealing operation is not often allowed to be done under the optimal conditions.
(3) Since the ultraviolet ray emitting instrument is located above the package base and applies the ultraviolet rays to the semiconductor package from above, the pincette pressing the lid becomes an obstacle to applying the ultraviolet rays on the overall surface of the semiconductor package uniformly. So, it results in lowering the sealing workability.
(4) Since the semiconductor package is directed upward during the sealing operation, the pincette pressing the lid may result in adhering dust to the semiconductor chip and causing damage to the lid surface.